In the subsea exploration and production of oil and gas it is highly advantageous to have an underwater structure located adjacent the seabed that is level relative to the surface of the water. The main reason for this is that various additional structures and lines are typically lowered from the surface and are more easily connectable to the underwater structure adjacent to the floor if that underwater structure is level. Examples of such underwater structures are drilling templates, production manifolds, wellhead temporary bases, guide means bases and flowline connector systems.
While prior art devices are known for levelling various structures adjacent to the floor of a body of water, these structures have numerous disadvantages. First, such devices usually require the placement of a plurality of support piles in the floor of the body of water, which is time consuming and expensive. Secondly, many of these prior art devices are dependent on the contour of the floor of the body of water since the structure must engage the floor; however, the floor is usually extremely irregular, thereby merely complicating the levelling activity. Thirdly, many of the prior art devices require complex level indication equipment. Another disadvantage of many of the prior art devices is that they require numerous steps which are time consuming and tie up the use of expensive surface vessels. Finally, many of the prior art levelling devices are capable of levelling only very small structures that cannot support large loads.
A solution to these problems of prior art levelling devices is to provide an underwater structure that is self-levelling; however, none are known to exist. On the other hand, there are self-levelling devices known in other fields which are disclosed in the following U.S. Pat. Nos. 22,378 to Red Head; 1,081,339 to Smith; 1,135,914 to Olesberg; 1,144,591 to Hellman; 1,661,993 to Borda; 1,915,466 to Lilly; 2,037,057 to Bartholomew; 2,161,718 to Miller; and 3,458,940 to Schmued. These patents do not, however, disclose viable systems for levelling underwater structures adjacent to the floor of a body of water.